c# 實現 HSV 調色板

界面相關核心代碼如下：

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            var rnd = new Random();
            var rgb = new ColorRGB(rnd.Next(0, 255), rnd.Next(0, 255), rnd.Next(0, 255));
            var hsv = ColorHelper.RgbToHsv(rgb);
            picDestinationColor.BackColor = Color.FromArgb(255, rgb.R, rgb.G, rgb.B);
            nudH.Value = hsv.H;
            nudS.Value = hsv.S;
            nudV.Value = hsv.V;
            refreshColorPanel(hsv);
            picPosH.Left = (int)(picH.Left + (picH.Width * nudH.Value / 360));
            picPosS.Left = (int)(picS.Left + (picS.Width * nudS.Value / 255));
            picPosV.Left = (int)(picV.Left + (picV.Width * nudV.Value / 255));
        }

        void refreshColorPanel(ColorHSV hsv)
        {
            var bm = new Bitmap(picH.Width, picH.Height);
            using (Graphics g = Graphics.FromImage(bm))
            {
                for (var i = 0; i < picH.Width; i++)
                {
                    var hsvColor = new ColorHSV(360 * i / picH.Width, 255, 255);
                    var rgbColor = ColorHelper.HsvToRgb(hsvColor);
                    var color = Color.FromArgb(255,rgbColor.R ,rgbColor.G ,rgbColor.B);
                    g.DrawLine(new Pen(color, 1), i, 0, i, picH.Height);
                }
                g.Save();
            }
            picH.Image = bm;

            bm = new Bitmap(picS.Width, picS.Height);
            using (Graphics g = Graphics.FromImage(bm))
            {
                for (var i = 0; i < picS.Width; i++)
                {
                    var hsvColor = new ColorHSV(hsv.H, 255 * i / picS.Width, hsv.V);
                    var rgbColor = ColorHelper.HsvToRgb(hsvColor);
                    var color = Color.FromArgb(255, rgbColor.R, rgbColor.G, rgbColor.B);
                    g.DrawLine(new Pen(color, 1), i, 0, i, picS.Height);
                }
                g.Save();
            }
            picS.Image = bm;

            bm = new Bitmap(picV.Width, picV.Height);
            using (Graphics g = Graphics.FromImage(bm))
            {
                for (var i = 0; i < picV.Width; i++)
                {
                    var hsvColor = new ColorHSV(hsv.H, hsv.S, 255 * i / picS.Width);
                    var rgbColor = ColorHelper.HsvToRgb(hsvColor);
                    var color = Color.FromArgb(255, rgbColor.R, rgbColor.G, rgbColor.B);
                    g.DrawLine(new Pen(color, 1), i, 0, i, picV.Height);
                }
                g.Save();
            }
            picV.Image = bm;

            var destRgbColor = ColorHelper.HsvToRgb(hsv);
            picDestinationColor.BackColor = Color.FromArgb(255, destRgbColor.R, destRgbColor.G, destRgbColor.B); ;
        }

        void colorChanged()
        {
            var hsv = new ColorHSV((int)nudH.Value, (int)nudS.Value, (int)nudV.Value);
            refreshColorPanel(hsv);
        }

        private void nudH_ValueChanged(object sender, EventArgs e)
        {
            colorChanged();
        }

        private void nudS_ValueChanged(object sender, EventArgs e)
        {
            colorChanged();
        }

        private void nudV_ValueChanged(object sender, EventArgs e)
        {
            colorChanged();
        }

        private void picH_MouseDown(object sender, MouseEventArgs e)
        {
            nudH.Value = (int)(360 * e.X / picH.Width);
            nudS.Value = nudS.Maximum;
            nudV.Value = nudV.Maximum;
            picPosH.Left = picH.Left + e.X;
        }

        private void picS_MouseDown(object sender, MouseEventArgs e)
        {
            nudS.Value = (int)(255 * e.X / picS.Width);
            picPosS.Left = picS.Left + e.X;
        }

        private void picV_MouseDown(object sender, MouseEventArgs e)
        {
            nudV.Value = (int)(255 * e.X / picV.Width);
            picPosV.Left = picV.Left + e.X;
        }
    }

    下面是實體類和一個工具類：

    #region RGB / HSV / HSL 顏色模型類
    /// <summary>
    /// 類      名：ColorHSL
    /// 功      能：H 色相 \ S 飽和度(純度) \ L 亮度 顏色模型 
    /// 日      期：2015-02-08
    /// 修      改：2015-03-20
    /// 作      者：ls9512
    /// </summary>
    public class ColorHSL
    {
        public ColorHSL(int h, int s, int l)
        {
            this._h = h;
            this._s = s;
            this._l = l;
        }

        private int _h;
        private int _s;
        private int _l;

        /// <summary>
        /// 色相
        /// </summary>
        public int H
        {
            get { return this._h; }
            set
            {
                this._h = value;
                this._h = this._h > 360 ? 360 : this._h;
                this._h = this._h < 0 ? 0 : this._h;
            }
        }

        /// <summary>
        /// 飽和度(純度)
        /// </summary>
        public int S
        {
            get { return this._s; }
            set
            {
                this._s = value;
                this._s = this._s > 255 ? 255 : this._s;
                this._s = this._s < 0 ? 0 : this._s;
            }
        }

        /// <summary>
        /// 飽和度
        /// </summary>
        public int L
        {
            get { return this._l; }
            set
            {
                this._l = value;
                this._l = this._l > 255 ? 255 : this._l;
                this._l = this._l < 0 ? 0 : this._l;
            }
        }
    }

    /// <summary>
    /// 類      名：ColorHSV
    /// 功      能：H 色相 \ S 飽和度(純度) \ V 明度 顏色模型 
    /// 日      期：2015-01-22
    /// 修      改：2015-03-20
    /// 作      者：ls9512
    /// </summary>
    public class ColorHSV
    {
        /// <summary>
        /// 構造方法
        /// </summary>
        /// <param name="h"></param>
        /// <param name="s"></param>
        /// <param name="v"></param>
        public ColorHSV(int h, int s, int v)
        {
            this._h = h;
            this._s = s;
            this._v = v;
        }

        private int _h;
        private int _s;
        private int _v;

        /// <summary>
        /// 色相
        /// </summary>
        public int H
        {
            get { return this._h; }
            set
            {
                this._h = value;
                this._h = this._h > 360 ? 360 : this._h;
                this._h = this._h < 0 ? 0 : this._h;
            }
        }

        /// <summary>
        /// 飽和度(純度)
        /// </summary>
        public int S
        {
            get { return this._s; }
            set
            {
                this._s = value;
                this._s = this._s > 255 ? 255 : this._s;
                this._s = this._s < 0 ? 0 : this._s;
            }
        }

        /// <summary>
        /// 明度
        /// </summary>
        public int V
        {
            get { return this._v; }
            set
            {
                this._v = value;
                this._v = this._v > 255 ? 255 : this._v;
                this._v = this._v < 0 ? 0 : this._v;
            }
        }
    }

    /// <summary>
    /// 類      名：ColorRGB
    /// 功      能：R 紅色 \ G 綠色 \ B 藍色 顏色模型
    ///                 所有顏色模型的基類，RGB是用於輸出到屏幕的顏色模式，所以所有模型都將轉換成RGB輸出
    /// 日      期：2015-01-22
    /// 修      改：2015-03-20
    /// 作      者：ls9512
    /// </summary>
    public class ColorRGB
    {
        /// <summary>
        /// 構造方法
        /// </summary>
        /// <param name="r"></param>
        /// <param name="g"></param>
        /// <param name="b"></param>
        public ColorRGB(int r, int g, int b)
        {
            this._r = r;
            this._g = g;
            this._b = b;
        }

        private int _r;
        private int _g;
        private int _b;

        /// <summary>
        /// 紅色
        /// </summary>
        public int R
        {
            get { return this._r; }
            set
            {
                this._r = value;
                this._r = this._r > 255 ? 255 : this._r;
                this._r = this._r < 0 ? 0 : this._r;
            }
        }

        /// <summary>
        /// 綠色
        /// </summary>
        public int G
        {
            get { return this._g; }
            set
            {
                this._g = value;
                this._g = this._g > 255 ? 255 : this._g;
                this._g = this._g < 0 ? 0 : this._g;
            }
        }

        /// <summary>
        /// 藍色
        /// </summary>
        public int B
        {
            get { return this._b; }
            set
            {
                this._b = value;
                this._b = this._b > 255 ? 255 : this._b;
                this._b = this._b < 0 ? 0 : this._b;
            }
        }

        /// <summary>
        /// 獲取實際顏色
        /// </summary>
        /// <returns></returns>
        public Color GetColor()
        {
            return Color.FromArgb(this._r, this._g, this._b);
        }
    }
    #endregion

/// <summary>
    /// 類      名：ColorHelper
    /// 功      能：提供從RGB到HSV/HSL色彩空間的相互轉換
    /// 日      期：2015-02-08
    /// 修      改：2015-03-20
    /// 作      者：ls9512
    /// </summary>
    public static class ColorHelper
    {
        /// <summary>
        /// RGB轉換HSV
        /// </summary>
        /// <param name="rgb"></param>
        /// <returns></returns>
        public static ColorHSV RgbToHsv(ColorRGB rgb)
        {
            float min, max, tmp, H, S, V;
            float R = rgb.R * 1.0f / 255, G = rgb.G * 1.0f / 255, B = rgb.B * 1.0f / 255;
            tmp = Math.Min(R, G);
            min = Math.Min(tmp, B);
            tmp = Math.Max(R, G);
            max = Math.Max(tmp, B);
            // H
            H = 0;
            if (max == min)
            {
                H = 0;
            }
            else if (max == R && G > B)
            {
                H = 60 * (G - B) * 1.0f / (max - min) + 0;
            }
            else if (max == R && G < B)
            {
                H = 60 * (G - B) * 1.0f / (max - min) + 360;
            }
            else if (max == G)
            {
                H = H = 60 * (B - R) * 1.0f / (max - min) + 120;
            }
            else if (max == B)
            {
                H = H = 60 * (R - G) * 1.0f / (max - min) + 240;
            }
            // S
            if (max == 0)
            {
                S = 0;
            }
            else
            {
                S = (max - min) * 1.0f / max;
            }
            // V
            V = max;
            return new ColorHSV((int)H, (int)(S * 255), (int)(V * 255));
        }

        /// <summary>
        /// HSV轉換RGB
        /// </summary>
        /// <param name="hsv"></param>
        /// <returns></returns>
        public static ColorRGB HsvToRgb(ColorHSV hsv)
        {
            if (hsv.H == 360) hsv.H = 359; // 360為全黑，原因不明
            float R = 0f, G = 0f, B = 0f;
            if (hsv.S == 0)
            {
                return new ColorRGB(hsv.V, hsv.V, hsv.V);
            }
            float S = hsv.S * 1.0f / 255, V = hsv.V * 1.0f / 255;
            int H1 = (int)(hsv.H * 1.0f / 60), H = hsv.H;
            float F = H * 1.0f / 60 - H1;
            float P = V * (1.0f - S);
            float Q = V * (1.0f - F * S);
            float T = V * (1.0f - (1.0f - F) * S);
            switch (H1)
            {
                case 0: R = V; G = T; B = P; break;
                case 1: R = Q; G = V; B = P; break;
                case 2: R = P; G = V; B = T; break;
                case 3: R = P; G = Q; B = V; break;
                case 4: R = T; G = P; B = V; break;
                case 5: R = V; G = P; B = Q; break;
            }
            R = R * 255;
            G = G * 255;
            B = B * 255;
            while (R > 255) R -= 255;
            while (R < 0) R += 255;
            while (G > 255) G -= 255;
            while (G < 0) G += 255;
            while (B > 255) B -= 255;
            while (B < 0) B += 255;
            return new ColorRGB((int)R, (int)G, (int)B);
        }

        /// <summary>
        /// RGB轉換HSL
        /// </summary>
        /// <param name="rgb"></param>
        /// <returns></returns>
        public static ColorHSL RgbToHsl(ColorRGB rgb)
        {
            float min, max, tmp, H, S, L;
            float R = rgb.R * 1.0f / 255, G = rgb.G * 1.0f / 255, B = rgb.B * 1.0f / 255;
            tmp = Math.Min(R, G);
            min = Math.Min(tmp, B);
            tmp = Math.Max(R, G);
            max = Math.Max(tmp, B);
            // H
            H = 0;
            if (max == min)
            {
                H = 0;  // 此時H應為未定義，通常寫為0
            }
            else if (max == R && G > B)
            {
                H = 60 * (G - B) * 1.0f / (max - min) + 0;
            }
            else if (max == R && G < B)
            {
                H = 60 * (G - B) * 1.0f / (max - min) + 360;
            }
            else if (max == G)
            {
                H = H = 60 * (B - R) * 1.0f / (max - min) + 120;
            }
            else if (max == B)
            {
                H = H = 60 * (R - G) * 1.0f / (max - min) + 240;
            }
            // L 
            L = 0.5f * (max + min);
            // S
            S = 0;
            if (L == 0 || max == min)
            {
                S = 0;
            }
            else if (0 < L && L < 0.5)
            {
                S = (max - min) / (L * 2);
            }
            else if (L > 0.5)
            {
                S = (max - min) / (2 - 2 * L);
            }
            return new ColorHSL((int)H, (int)(S * 255), (int)(L * 255));
        }

        /// <summary>
        /// HSL轉換RGB
        /// </summary>
        /// <param name="hsl"></param>
        /// <returns></returns>
        public static ColorRGB HslToRgb(ColorHSL hsl)
        {
            float R = 0f, G = 0f, B = 0f;
            float S = hsl.S * 1.0f / 255, L = hsl.L * 1.0f / 255;
            float temp1, temp2, temp3;
            if (S == 0f) // 灰色
            {
                R = L;
                G = L;
                B = L;
            }
            else
            {
                if (L < 0.5f)
                {
                    temp2 = L * (1.0f + S);
                }
                else
                {
                    temp2 = L + S - L * S;
                }
                temp1 = 2.0f * L - temp2;
                float H = hsl.H * 1.0f / 360;
                // R
                temp3 = H + 1.0f / 3.0f;
                if (temp3 < 0) temp3 += 1.0f;
                if (temp3 > 1) temp3 -= 1.0f;
                R = temp3;
                // G
                temp3 = H;
                if (temp3 < 0) temp3 += 1.0f;
                if (temp3 > 1) temp3 -= 1.0f;
                G = temp3;
                // B
                temp3 = H - 1.0f / 3.0f;
                if (temp3 < 0) temp3 += 1.0f;
                if (temp3 > 1) temp3 -= 1.0f;
                B = temp3;
            }
            R = R * 255;
            G = G * 255;
            B = B * 255;
            return new ColorRGB((int)R, (int)G, (int)B);
        }
    }